[Intel-gfx] [PATCH 78/89] drm/i915/skl: Flush the WM configuration

[Damien Lespiau]

When we write new values for the DDB allocation and WM parameters, we now
need to trigger the double buffer update for the pipe to take the new
configuration into account.

As the DDB is a global resource shared between planes, enabling or
disabling one plane will result in changes for all planes that are
currently in use, thus the need write PLANE_SURF/CUR_BASE for more than
the plane we're touching.

v2: Don't wait for pipes that are off

v3: Split the staging results structure to not exceed the 1Kb stack
    allocation in skl_update_wm()

Signed-off-by: Damien Lespiau <damien.lespiau at intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 92 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 7f7a2e2..d378879 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3198,6 +3198,22 @@ static bool skl_ddb_allocation_changed(const struct skl_ddb_allocation *new_ddb,
 	return false;
 }
 
+static unsigned int
+skl_ddb_pipe_allocation_size(const struct skl_ddb_allocation *ddb,
+			     const struct intel_crtc *intel_crtc)
+{
+	struct drm_device *dev = intel_crtc->base.dev;
+	unsigned int size = 0;
+	enum pipe pipe = intel_crtc->pipe;
+	int plane;
+
+	for_each_plane(pipe, plane)
+		size += skl_ddb_entry_size(&ddb->plane[pipe][plane]);
+	size += skl_ddb_entry_size(&ddb->cursor[pipe]);
+
+	return size;
+}
+
 static void skl_compute_wm_global_parameters(struct drm_device *dev,
 					     struct intel_wm_config *config)
 {
@@ -3434,6 +3450,81 @@ static void skl_write_wm_values(struct drm_i915_private *dev_priv,
 	}
 }
 
+static void skl_wm_flush_pipe(struct drm_i915_private *dev_priv, enum pipe pipe)
+{
+	struct drm_device *dev = dev_priv->dev;
+	int plane;
+
+	for_each_plane(pipe, plane) {
+		I915_WRITE(PLANE_SURF(pipe, plane),
+			   I915_READ(PLANE_SURF(pipe, plane)));
+	}
+	I915_WRITE(CURBASE(pipe), I915_READ(CURBASE(pipe)));
+}
+
+static void skl_flush_wm_values(struct drm_i915_private *dev_priv,
+				struct skl_wm_values *new_values)
+{
+	struct drm_device *dev = dev_priv->dev;
+	struct skl_ddb_allocation *cur_ddb, *new_ddb;
+	unsigned int cur_size[I915_MAX_PIPES], new_size[I915_MAX_PIPES];
+	struct intel_crtc *crtc;
+	enum pipe pipe;
+
+	new_ddb = &new_values->ddb;
+	cur_ddb = &dev_priv->wm.skl_hw.ddb;
+
+	/*
+	 * Start by computing the total allocated space for each pipe as we
+	 * need that values for the two passes.
+	 */
+	for_each_intel_crtc(dev, crtc) {
+		pipe = crtc->pipe;
+		new_size[pipe] = skl_ddb_pipe_allocation_size(new_ddb, crtc);
+		cur_size[pipe] = skl_ddb_pipe_allocation_size(cur_ddb, crtc);
+	}
+
+	/*
+	 * First pass: we flush the pipes that had their allocation reduced.
+	 *
+	 * We then have to wait until the pipe stops fetching pixels from the
+	 * previous allocation. This way, pipes that have just been allocated
+	 * more space won't try to fetch pixels belonging to a different pipe.
+	 */
+	for_each_intel_crtc(dev, crtc) {
+		if (!crtc->active)
+			continue;
+
+		pipe = crtc->pipe;
+
+		if (new_size[pipe] < cur_size[pipe]) {
+			skl_wm_flush_pipe(dev_priv, pipe);
+			intel_wait_for_vblank(dev, pipe);
+		}
+	}
+
+	/*
+	 * Second pass: flush the pipes that got more allocated space.
+	 *
+	 * We don't need to actively wait for the update here, next vblank
+	 * will just get more DDB space with the correct WM values.
+	 */
+	for_each_intel_crtc(dev, crtc) {
+		if (!crtc->active)
+			continue;
+
+		pipe = crtc->pipe;
+
+		if (new_size[pipe] < cur_size[pipe])
+			continue;
+
+		if (!skl_ddb_allocation_changed(new_ddb, crtc))
+			continue;
+
+		skl_wm_flush_pipe(dev_priv, pipe);
+	}
+}
+
 static bool skl_update_pipe_wm(struct drm_crtc *crtc,
 			       struct skl_pipe_wm_parameters *params,
 			       struct intel_wm_config *config,
@@ -3525,6 +3616,7 @@ static void skl_update_wm(struct drm_crtc *crtc)
 
 	skl_update_other_pipe_wm(dev, crtc, &config, results);
 	skl_write_wm_values(dev_priv, results);
+	skl_flush_wm_values(dev_priv, results);
 
 	/* store the new configuration */
 	dev_priv->wm.skl_hw = *results;
-- 
1.8.3.1